The devices known in the art for bending metallic strips, in particular those intended for the production of die-cutting blades, generally include a system for feeding the continuous metallic strip through a guide aperture, in the vicinity of which one or more bending tools are located. In the majority of cases two bending tools are provided, one to bend the strip to the right (or upwards, for example) and the other to bend the strip to the left (or downwards, for example).
The strip is fed forward through the guide aperture and temporarily stopped to perform the bending operation. The bending tool to be used is positioned near the guide aperture and then rotated to deform the strip as required to the right (or left) at a pre-set angle.
A bending system with two tools is described, for example, in U.S. Pat. No. 5,870,919, in which the bending tools are retractable tools engaged in appropriate seats of coaxial supporting elements and rotated around their common axis. The bending tools can be used in a mutually exclusive way, i.e. keeping one tool in the work position (extended) while the other is kept in the rest position (retracted) and vice versa.
Another example of a bending system with two tools is described in the U.S. Pat. No. 6,629,442, in which each tool is supported by a pair of coaxial supporting elements which can rotate around their common axis. The supporting elements of a pair are arranged alternately with those of the other pair and, consequently, at least two of them must have a seat for engagement of the bending tool supported, and a groove to permit the movement of the other one.
During the bending action, sliding occurs between the tool in contact with the strip and the strip itself. This results in considerable wear of the bending tools and therefore the need to replace the tools fairly frequently to ensure the necessary working accuracy.
It should also be remembered that during the bending step, the tool is subject to a stress which increases proportionally to the bending angle required. The effects of wear on the tool are therefore considerable if strips have to be produced with particularly narrow bending angles.
The known systems described above are particularly complex from the mechanical point of view and, consequently, replacement of the bending tools can be particularly time-consuming, thus affecting productivity.
Independently of the wear on the tools, the feed section of the strip, with the relative guide aperture, also has to be changed whenever starting a new production phase with a metallic strip with dimensions or shape different from that of the strip processed previously.
In general, the object of the present invention is to propose a device and a process for bending metallic strips which overcome the drawbacks of the known technique.
A particular object of the present invention is to propose a device of the type described above which is mechanically simple to produce.
A further object of the present invention is to propose a device of the type described above which makes the operations for replacing the bending tools and/or the strip feed section quick and easy.